This invention relates generally to the field of container closures, and more particularly to an improved safety type closure or cap adapted to effect a substantially tight seal with respect to the mouth of the container.
As defined by National Formulary, since NF 7 effective from 1942, a "well closed" container protects the content of the container from extraneous solids and from loss of the contents under ordinary or customary conditions of handling, shipment, storage and distribution.
By contrast, a "tight" container protects the contents from contamination by extraneous liquids, solids and vapors, from loss of a drug, and from efforescence, deliquescence or evaporation under the ordinary or customary conditions of handling, shipment, storage and distribution, and, additionally, is capable of tight reclosure. As a general rule, a tight container must offer moisture, permeability some 20 times less than a "well closed" container.
More recently, because of increased standards of safety from the standpoint of discovery and appropriation of the contents by children of tender years, container closures have been designed to require knowledgeable manipulation on the part of the user to open the closure, as a result of which recourse to the screw thread type of closure has been severely limited when a "tight" closure is required.
The most common type of safety closure employs a peripheral rim having a least one interrupted segment. A corresponding projection on the cap is rotatably aligned with the interrupted segment during the opening procedure, following which the cap may be lifted at this point to pivot the cap from the container. An example of this type of closure is disclosed in U.S. Pat. No. 3,669,295 of June 13, 1972, granted to William Horvath. Unlike screw type closures, in which the degree of tightness of the closure depends upon the degree the cap is twisted relative to the container, snap type caps have a uniform degree of tightness which depends, among other factors, upon the degree of distortion imparted to the synthetic resinous components of the cap, and the elastic modulus of the material from which the cap is made. While it is possible to manufacture threaded type safety caps, included a freely turning outer shell which is engaged with an inner element upon the application of axially directed pressure upon the shell, such constructions are expensive, and require the provision of a resilient jacket of compressible material lining the end wall of the cap.
In the U.S. Pat. No. 4,087,016 to Townes, et al., granted Apr. 2, 1978, and assigned to the same asignee as the assignee of the present application, there is disclosed a tightly sealing safety cap which may be utilized in conjunction with either a synthetic resinous or glass container which fulfills substantially all of the above mentioned criteria. However, in recent years there has been a growing tendency to manufacture the container from a synthetic resinous material which possesses a substantial degree of resiliency, albeit far less than that of the cap. Where the container is of relatively small size, as is often the case when the container is used for storage of prescription drugs, it is possible for children of tender years to attempt to remove the cap by inserting the open end of the container into the mouth so as to be engaged between the jaws of the child. Children of even tender years normally possess very powerful jaws, and are capable of distorting the cross sectional shape of the container from circular to ovate, often to a degree which sufficiently lessens the purchase of the cap upon the container, to permit the child to further flex the cap and remove it from engagement of the container without the necessity of aligning the usual index means with a corresponding vertical slot in the flange surrounding the mouth of the container. It is an object of the present invention to provide improved cap construction which will eliminate the possibility of such disengagement.